1. FIELD OF THE INVENTION
The present invention relates to highway sign supports, and particularly to a coupler for attachment of a highway sign post to a ground or anchor post, the coupler having a shear section which causes the sign post to break away from the ground post upon impact by a motor vehicle.
2. DESCRIPTION OF THE RELATED ART
In recent years state and local highway departments have become uncreasingly concerned with safety of vehicle passengers. Highway signs can cause great injury if struck by a car, truck, or other vehicles. Passenger cars, even while traveling at low speeds, can cause terrific impact to road side sign posts when struck. Such sign posts may cause damage to the vehicle, the occupants of the vehicles, and pedestrians.
Conventional breakaway sign posts generally have a sign post which is U-shaped in cross section with a relatively short, separate ground post which is driven into the ground connected to the sign post by a breakaway section. The longer, upper sign post section to which the sign is attached, extends vertically some eight to ten feet. The breakaway device joins the two post sections and when struck by a vehicle, the breakaway mechanism car be replaced and the sign may be restored to its previous position.
Many prior art devices have utilized shear pins which will break upon a calculated amount of applied force, as from careening vehicle. However, since shear pins can be incorrectly used or replaced by inexperienced workers, either the sign post may fail before the breakaway section or the breakaway section may fail to operate as intended.
U.S. Pat. No. 4,759,161, issued Jul. 26, 1988 to Kucyk, Jr., et al., describes a breakaway sign post which includes a foundation post having a projection and a sign post mounted on the projection by a sleeve. A shear pin extends transversely through the sleeve, and preferably also through an eyebolt mounted on the projection, the eyebolt also having a shear point between the eye and the shaft.
U.S. Pat. No. 4,850,565, issued Jul. 25, 1989 to A. M. Moreno, shows a ground post with a U-shaped channel at the top of the post with a first cylindrical member welded inside the channel, a U-shaped channel having a second cylindrical member welded to the inside of the channel, and a shear pin extending through aligned bores in the first and second cylindrical members. U.S. Pat. No. 4,858,876, issued August 22, 1989, also to Moreno, discloses a similar structure in which the intermediate portion of the shaft of the shear pin is hexagonal in cross section.
U.S. Pat. No. 5,214,886, issued Jun. 1, 1993 to D. P. Hugron, shows a breakaway connector having a cross sectional shape identical to the cross sections of the sign post and the ground post, the connector being bolted to the sign post and the ground post and having a section between the two posts weakened by a groove which is horizontal through the web and side walls, but vertical in the fold between the side walls and the flanges. Part of the connector breaks on impact, but the sign post and ground post are not completely severed.
U.S. Pat. No. 5,425,593, issued Jun. 20, 1995 to R. J. Buehler, discloses a sleeve for connecting the sign post to the ground post, the sleeve having upper and lower receptacles, the posts being partly disposed within the receptacles. One of the embodiments, shown in FIG. 20, has a narrowed diameter for easy breakaway. It will be noted that the invention in Buehler is not described as a breakaway coupler, but as a sleeve for connecting one post to the other, regardless of how the posts became separated. It will be further noted that the description of the embodiment shown in FIG. 20 of the Buehler patent does not specify the materials from which it is made, does not describe the narrowed diameter as being hollow, does not describe a bore extending through the coupler longitudinally, and does not describe any slots defined in the receptacles.
U.S. Pat. No. 5,480,121, issued Jan. 2, 1996 to Rice, et al., describes a breakaway connector having two U-shaped sections bolted to the sign post and the ground post, the U-shaped sections being joined by a hollow stud welded to the web of each connector. The hollow stud has an annular groove about its center and two aligned bores extending transversely through the groove. U.S. Pat. No. 4,862,823, issued Sep. 5, 1989 to R. K. Hughes, teaches signs for marking boundaries which bend when struck by a reel type lawn mower, the sign having a ground section and a sign section joined by a flexible sleeve.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a sign post coupler solving the aforementioned problems is desired.